Police say a teenage fraternity brother's night out with family in Florida somehow spiraled into an horrific double stabbing that ended with the suspect chewing off his victim's face.

The Martin County Sheriff's Office says Austin Harrouff, a 19-year-old Alpha Delta Phi brother at Florida State University, was found biting at the face of John Stevens, 59, at his Tequesta home late Monday.

Nearby was the body of Michelle Mishcon, 53, who police believe Harrouff also killed after allegedly targeting the couple at random.

It's possible Harrouff was under the influence of an hallucinogenic drug such as flakka or bath salts when police say they found him biting chunks from the flesh on Stevens' face, according to Martin County Sheriff William Snyder.

The teen, who has no criminal record, was eating dinner with his family not far from Stevens' home when he reportedly stormed out angry over slow service.

Harrouff (middle row, third from left) was a sophomore in the Alpha Delta Phi frat at Florida State. He had no prior criminal record.

The teen's family was so concerned about Harrouff's behavior that they called police and his fraternity brothers to try to find him.

Not far from the restaurant after 9:00 p.m., a would-be rescuer called 911 to report an attack. The good Samaritan was injured so badly that he was airlifted to a hospital where he underwent emergency surgery, WPEC reports.

Meanwhile, a responding officer at the scene first tried to use a Taser on Harrouff, who was unaffected. Police said it eventually took multiple deputies and a K-9 to pry Harrouff off the victim.

When police first approached him, they say Harrouff gave them a false name.

A knife was reportedly discovered at the scene. However, Snyder said the victims suffered so many stab wounds and blunt force trauma that investigators may never be entirely sure if it's the precise murder weapon.

Stevens' home is not far from Harrouff's father's house, Snyder said. Police believe Harrouff chose to take a different road one street away from where his father lived, allegedly leading him to the scene of the crime.

Police believe there is no connection between Harrouff and the victims.

Snyder said Harrouff was "making animal-like sounds" after he was taken to a hospital for treatment. At a press conference held Tuesday afternoon, Snyder revealed that Harrouff is listed in "grave condition," potentially due to something he ingested.

"The suspect in this case was abnormally strong," Snyder said. While Snyder said tests showed no signs of meth, cocaine, heroin or other common drugs, it will take longer to test for less common substances like flakka or bath salts.

Harrouff is a sophomore at Florida State University in Tallahassee. The Jupiter, Florida, native attended Suncoast Community High School where he wrestled and played football.

A spokesperson with the Martin County Sheriff's Office said Harrouff was still in an area hospital Tuesday afternoon.